Mixed-Mode Fuel Injector with a Variable Orifice

ABSTRACT

The invention disclosed a mixed-mode fuel injector with micro-variable-circular-orifice (MVCO), which is a fuel injection device for internal combustion engines, either diesel or gasoline engines. The fuel injector is a high-accuracy couple of components comprising a needle valve ( 1 ) and a nozzle body ( 5 ). Said needle valve is movable back and forth and received in said nozzle body to provide an opening position for fuel injection and a biased closing position. Said nozzle body has multiple-micro-channels ( 6 ) on the inner conical surface (C) close to the tip of the nozzle body. The injector has a MVCO ( 4 ) comprising a micro-variable-circular aperture and multiple-micro-channels, and has means of generating variable mixed-mode sprays of conical and multi-jet shapes, with a major homogeneous conical spray at low to medium injection loads.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a mixed-mode fuel injector with amicro-variable-circular-orifice (MVCO) and homogeneous atomization, andparticularly to a fuel injector for a direct injection internalcombustion engine, which can be either a spark-ignition gasoline engineor a compression-ignition diesel engine. The current filing is focusedon the nozzle part of the fuel injector.

2. Description of the Related Art

The combustion process in a conventional direct injection Diesel engineis characterized by diffusion combustion with a multi-hole fuelinjector. Due to its intrinsic non-homogeneous characteristics offuel-air mixture formation, it is often contradictory to simultaneouslyreduce soot and NOx formation in a conventional diesel engine. Over lasttwo decades, significant progress has been made for Diesel enginecombustion (U.S. Pat. Nos. 4,779,587, 6,230,683), but further reducingemissions from Diesel engines to comply upcoming emission legislationsstill remains a challenge. Progress has been made in recent years forresearch of Homogeneous-Charge Compression-Ignition (HCCI) combustionengines. However, many issues remain to be solved to have a practicalapproach to control the ignition timing, the duration of combustion, therate of combustion for HCCI engine for various load conditions. Currentengine control strategies, such as U.S. Pat. No. 6,230,683, areeffective but very complex and will increase the cost for applications.It seems more a viable solution to operate engine in a mixed-mode, or inHCCI mode or quasi-HCCI mode at low to medium loads, and in conventionalspray combustion mode at high loads for the near future. It would bedesirable to design a fuel injector which is suitable for this type ofmixed-mode combustion, at least to provide most features desired byoptimal engine combustion.

To improve combustion at the full load range, fine atomization withaccurate control of doses and timing is needed. A well-known current artfor improving atomization is to increase the number of holes of nozzlesand decrease the diameter of nozzle holes, and use piezo actuators andhigh common rail pressure (U.S. Pat. Nos. 6,726,121, 6,557,779), such asBOSCH's piezo-injector with coaxial-vario-nozzle (Roger Busch, AdvancedDiesel Common Rail Injection System for Future Emission Legislation,Diesel Engine Emission Reduction Conference, August, 2004, Coronado,Calif.). Such an approach, while it's effective for improvingatomization and combustion, it does, at the same time, mandate a verycomplex structure and a much higher rail pressure, thus increase thepower needed for fuel pump and manufacture cost of fuel systems, andincrease the potential risks of fuel leaking.

3. Objectives and Advantages

Accordingly, several objectives and advantages of the invention are: (1)the micro-variable-circular-orifice (MVCO) is equivalent to a connectionof infinite number of micro-holes, thus said fuel injector can form avariable micro aperture for fine atomization and ensure high fuelinjection rate simultaneously. It enables using a single needle valvewith micro lift, which is desired for working with a piezo actuator orhydraulic pressure amplifier to accurately control the fuel injectiondose, atomization quality and give a much shorter response time. (2)said fuel injector, through its variable nature of injection sprays,provides a homogeneous fine atomization at low to medium loads, thus itis favorable for HCCI combustion mode, and provides fine atomization andsufficient penetration at high engine loads, thus it ensures enginepower output. The varying micro-variable-circular-orifice (MVCO) featurecan provide different sizes of the fuel injection exit cross-sectionarea of the injector, which is superior to a conventional nozzle withfixed injection hole cross-section area, thus said MVCO can providedifferent fuel atomization rate and SMD (Sauter Mean Diameter) based onneeds for optimal combustion for different load and speed conditions.(3) Since the micro-variable-circular-orifice (MVCO) keeps varyingduring the fuel injection process, the needle valve has self-cleaningeffect, it is more robust for eliminating clogging. This featureimproves reliability of fuel injection systems, it has more advantagesthan a conventional multi-hole nozzle, which is prone to get clogged incertain operating conditions and has heavy injection pressure loss wheninjection holes are too small. (4) The special design of the flowchannel in the injector reduces pressure loss comparing with aconventional multi-hole nozzle through its novel fuel passage designnear the MVCO, thus reduces the demand for extremely high rail pressureas required by small multi-hole nozzle, and reduces required fuel pumppower. (5) Given many desirable features' for combustion, said fuelinjector also has a relatively simple structure, instead of a complexstructure with two needle valves, it uses a single needle valve togenerate mixed-mode sprays through novel orifice design. It can savemanufacturing cost. Said fuel injector provides a key device for meetingthe current and future engine emission regulations.

SUMMARY OF THE INVENTION

This invention provides a novel design of a mixed-mode fuel injector formixed-mode HCCI-conventional combustion, more specifically a novelnozzle with a micro variable circular aperture and micro-channels toreduce pressure loss in the injector channel and provide a homogeneousinitial fuel distribution. The mixed-mode fuel injector can generate ahomogeneous fine atomization with sufficient penetration without relyingon excessive high rail pressure. The fuel injector is a high-accuracycouple of components with a needle valve and a nozzle body, which systemhas a micro-variable-circular-orifice (MVCO) comprising a variablecircular aperture between needle valve and nozzle body and multiplemicro-channels on the inner conical surface closing to the nozzle bodytip. The fuel injector is capable of generating variable mixed-modesprays of conical and multi-jet shapes, with a major circularlyhomogeneous conical spray at low to medium engine loads, and mixed-modesprays composed of a conical spray and multi-jets at high loads. Themixed-mode-spray ensures homogeneous atomization and sufficientpenetration simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary sectional view of a first exemplary embodimentof an injector of the invention;

FIG. 2 is an amplified fragmentary sectional view of FIG. 1 for themicro-variable-circular-orifice (MVCO);

FIG. 3 is a bottom-up view of FIG. 1 for themicro-variable-circular-orifice (MVCO);

FIG. 4 is an illustration of the mixed-mode conical-multi-jet spraygenerated by the embodiment of the fuel injector illustrated in FIG. 1;

FIG. 5 is a fragmentary three-dimensional view of the fuel injector inFIG. 1;

In all the figures, 1—needle valve; 2—needle sealing surface; 3—needlehead; 4—micro-variable-circular-orifice (MVCO) (including a circularaperture and micro channels); 5—nozzle body; 6—micro fuel channels;7—tip surface of the nozzle body; A —up-rim of the needle head; B—theintersection of the needle head outer surface (or its extension) and tipsurface of nozzle body; C—conical surface at the tip surface of thenozzle body; D—inner hole of the tip of the nozzle body; F—drivingmeans, which can be active means provided by solenoid or piezoactuators, or a passive means by fuel pressure; S—high pressure fuelsupply.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The mixed-mode fuel injector is a high-accuracy couple of componentswith a needle valve (1 in FIG. 2), which has a conical head for guidingfuel sprays, which has an opening and a biased closing position, whichis movable back and forth and received in a nozzle body (5 in FIG. 2).The fuel injector has a micro-variable-circular-orifice (MVCO) (4 inFIG. 2) comprising of a variable circular ring aperture between saidneedle valve (1) and said nozzle body (5) and multiple micro-channels(6) on the inner conical surface (C) closing to the nozzle body tip(FIG. 1, FIG. 2, FIG. 3). Said needle valve is received in said nozzlebody and has a biased closing position and an opening position decidedby driving means such as actuators, when said needle valve is at itsopening positions, fuel is discharged through said MVCO. The fuelinjector is capable of generating variable mixed-mode sprays of conicaland multi-jet shapes (FIG. 4), whereby generating a major circularlyhomogeneous conical spray at low to medium loads, and variablemixed-mode fuel sprays at high loads to ensure homogeneous atomizationand sufficient penetration. Depending on the location of themicro-channels and whether the micro-channels are open channels orclosed channels simply like conventional nozzle-holes, it can formdifferent versions of spray shapes to satisfy different needs ofpenetration and atomization.

The mixed-mode fuel injector, wherein the needle lift is micro-motionwith a range approximately 0-300 μm, the included angle of the conicalsealing surface (2) at the nozzle body is approximately between 50-70degree, the needle head diameter (d₃) is between 0.8-3.5 mm, the anglebetween the centerline of the nozzle body and the inner conical surface(C) at the nozzle body tip is approximately in the range of 35-75degree.

A fuel injector, as a simplified version or alternative of saidmixed-mode fuel injector (FIG. 2), wherein close to the tip surface (7)of nozzle body there is a conical surface (C), which is a smoothsurface, the conical surface can be a single conical surface, or can bean integrated conical surface comprising two or more conical surfaceswith different conical angles, or a diverging curve surface, the upperrim (A) of the needle head (3) is merged in the tip surface (7) of thenozzle body during the needle lifting, the needle head (3) can bepartially or wholly merged in the tip surface (7) of the nozzle bodyduring the needle lifting, when the needle valve is lifted, fuel isinjected through the aperture (4) between the needle head and conicalsurface (C) of the nozzle body.

The mixed-mode fuel injector (FIG. 2), wherein close to the tip surface(7) of nozzle body there is a conical surface (C), the conical surfacecan be a single conical surface, or can be an integrated conical surfacecomprising two or more conical surfaces with different conical angles,or a diverging curve surface, the conical surface close to the needlevalve is a surface with multiple micro-channels (6) with the shape ofsemi-circle, arcs, triangle, trapezoid or other polygons, or withhelical micro-channels, the upper rim (A) of the needle head (3) ismerged in the tip surface (7) of the nozzle body (5) during the needlelifting, the needle head can be partially or wholly merged in the tipsurface (7) of the nozzle body during the needle lifting, when theneedle valve is lifted, fuel is injected through the variable aperturebetween the needle head and conical surface (C) of the nozzle body, fuelis also injected through the multiple micro-channels (6). The uppersurface of the needle head (3) and the conical surface (C) serves asguiding surfaces for sprays.

The mixed-mode fuel injector, wherein the fuel channel between theneedle head (3) and conical surface (C) of the nozzle body is ofconverging-diverging nozzle shape, due to micro-needle-lift of theneedle valve, the lifted minimum dimension of the aperture of thechannel is approximately in the range of 30-125 μm, the minimum apertureis at the sealing surface (2) during the early stage of fuel injection.The minimum aperture is at the needle valve exit injection-cross-section(4) or at the sealing surface (2), depending on a specific design,during the middle stage of fuel injection, and the minimum aperture isat the sealing surface again during the late stage of fuel injection.During all fuel injection stages, the minimum aperture is approximatelyless than 125 μm, thus ensures fine atomization during all fuelinjection stages.

The mixed-mode fuel injector, wherein the depth of conical surface (C)close to the nozzle exit is approximately in the range of 0.15-3 mm, theconical angle of conical surface (C) is approximately in the range of80-150 degree.

The mixed-mode fuel injector (FIG. 1, FIG. 2), wherein there areapproximately 4-20 micro-channels (6) with the cross-section shape ofeither semi-holes with the diameters approximately in the range of50-300 μm, or other shapes as described above with the maximum dimensionapproximately between 50-400 μm (i.e., the geometric cross section ofsuch a channel can fit in a circle with a diameter of 50-400 μm), thesizes of these micro-channels can be the same or varying depending onspecific needs of atomization, these micro-channels can be homogeneouslyor non-homogeneously distributed on the conical surface (C).

The mixed-mode fuel injector, wherein at low to medium engine loads,fuel is mainly injected through the variable circular aperture betweensaid needle head and said nozzle body, thus mainly forms a conical shapespray, while at high loads, fuel is injected through both the variablecircular aperture and the micro-channels (6) on the conical surface (C),fuel forms mixed-mode conical-multi-jet shape sprays (FIG. 4), thusensures both fine atomization and sufficient penetration.

A special version of fuel injector as described above has means ofgenerating different shapes of fuel sprays by changing the magnitude oflift of said needle valve, wherein at low to medium injection loads,fuel is mainly injected through the variable circular aperture betweenthe needle head and nozzle body, thus mainly forms a conical shapespray, while at high injection loads, the needle head can completely orpartially block the variable circular aperture, whereby fuel is fully ormainly injected through the micro-channels, which can be open channelsor closed channels depending on penetration needs, thus mainly formsconventional multi-hole sprays at high loads, whereby provides differentpenetration desired by engine combustion at different loads.

A special version of fuel injector as described above has a plurality ofmicro-channels underneath the said conical surface with the crosssection shape of conventional nozzle holes, which can form sac-hole orvalve-covered-orifice multi-hole type injector through blocking thecircular aperture by the needle head at a predefined needle-lift range.

The mixed-mode fuel injector, wherein the angle between the centerlineof the conical surface (C) and the centerline of the nozzle body (5) isapproximately between 0-15 degree, depending on the angle between thecenterline of the fuel injector and the centerline of the piston in theengine cylinder.

The mixed-mode fuel injector, is intended but not limited to directinjection diesel engines, direct injection gasoline engines, or otherdirect injection alternative fuel engines, it is intended formechanical, electro-mechanical, piezo fuel injectors, or fuel injectorswith hydraulic pressure amplifiers. Said fuel injector can also be usedto inject other liquids, such as water, thus it can be used as a generalpurpose injector.

For small direct injection diesel engines, the major dimensions for themixed-mode fuel injector are approximately: d₁=3.0-5 mm; d₁-d₂=0.3-0.8mm; d₃=0.8-2.5 mm; the diameter of nozzle body hole—d₃=10-18 μm; theincluded angle at sealing surface at nozzle body=50-75 degree; theneedle-lift range=30-240 μm; the cone angle of the conical surface atthe tip of nozzle body=100-150 degree; the number of micro channels onthe conical surface (C)=6-18; the maximum dimension of the microchannels (6)=50-280 μm.

For medium size direct injection diesel engines, the major dimensionsfor the mixed-mode fuel injectors are: d₁=4-6 mm; d₁-d₂=0.4-0.8 mm;d₃=1.0-3.0 mm. The cone angle of the conical surface (C)=120-150 degree;the maximum dimension of the micro channels (6)=50-400 μm; otherparameters are similar to small diesel engines. The rail pressure forsaid mixed-mode fuel injector is about 800-1200 bar. While higherpressure is better, it is not mandated for fine atomization. The openinjection pressure is approximately 240 bar or higher.

The mixed-mode fuel injector is intended for but not limited to internalcombustion engines. The outer surface of the nozzle body can be ofcylindrical, conical, or converging-diverging shape.

Those who are skilled in the art will find that it's easy to make minorchanges to the nozzle structure following the same design concept inthis invention, such as adding micro-channels or adding spirals on theneedle head or on the conical surface (C) of the nozzle body, theseramifications are within the scope of this invention.

1. A mixed-mode fuel injector comprising: (i) a nozzle body (5)comprising passages for fuel, an, inner cylindrical space for receivinga needle valve, and a conical surface (C) close to the tip (7) of thenozzle body for guiding a spray of fuel; (ii) a needle valve (1), whichhas a converging-diverging conical head for guiding a spray of fuel andwhich is movable back and forth and received in said nozzle body,wherein said needle valve is at a biased closing position or an openingposition defined by driving means; and (iii) amicro-variable-circular-orifice (4) comprising a variable circular ringaperture between said needle valve and said nozzle body, such that fuelis dischargeable in variable sprays of conical and conical-multi-jetshapes through said micro-variable-circular-orifice by lifting saidneedle valve at different magnitudes.
 2. A mixed-mode fuel injectoraccording to claim 1, wherein the micro-variable-circular-orifice (4)further comprises a plurality of micro-channels (6).
 3. A mixed-modefuel injector according to claim 1 or 2, wherein the conical surface (C)has a single conical surface.
 4. A mixed-mode fuel injector according toclaim 1 or 2, wherein the conical surface (C) is an integrated conicalsurface having two or more conical surfaces with different conicalangles connected together.
 5. A mixed-mode fuel injector according toclaim 1 or 2, wherein the conical surface (C) is a diverging curvedsurface.
 6. A mixed-mode fuel injector according to claim 1 or 2,wherein the needle lift for the opening position is approximately in therange of 0-300 μm, the needle head diameter is approximately in therange of 0.8-3.5 mm, and the angle between the centerline of the nozzlebody (5) and the inner conical surface (C) at the nozzle body tip (7) isapproximately in the range of 35-75 degrees.
 7. A mixed-mode fuelinjector according to claim 2, wherein the plurality of micro-channels(6) is on the said conical surface (C) with cross sections that are oneor more of semi-circles, arcs, triangles, trapezoids or other polygons.8. A mixed-mode fuel injector according to claim 2, wherein the needlehead (3) remains at least partially received within the tip (7) as theneedle valve (1) is moved back and forth between the biased closingposition and opening position such that when fuel is injected throughthe micro variable aperture (4) between the needle head and said conicalsurface of the nozzle body, fuel is also injected through the multiplemicro-channels (2), the upper surface of the needle head and the conicalsurface serve as guiding surfaces for fuel sprays.
 9. A mixed-mode fuelinjector according to claim 7, wherein there are about 4-20micro-channels (6) with the cross-section of semi-circles with thediameters approximately in the range of 50-300 μm.
 10. A mixed-mode fuelinjector according to claim 7, wherein there are about 4-20micro-channels (6) having a cross-section other than semi-circles withthe maximum dimension approximately between 50-400 μm.
 11. A mixed-modefuel injector according to any of claims 2 to 10, wherein the sizes ofsaid micro-channels (6) are the same.
 12. A mixed-mode fuel injectoraccording to any of claims 2 to 10, wherein the sizes of themicro-channels (6) are different depending on specific needs ofatomization.
 13. A mixed-mode fuel injector according to any of claims 2to 12, wherein the said micro-channels (6) are distributed on or underthe conical surface (C) so that they are open channels or closedchannels.
 14. A mixed-mode fuel injector according to claim 2, has aplurality of micro-channels underneath the said conical surface (C),forming a sac-hole or valve-covered-orifice multi-hole type injectorthrough blocking the circular aperture by the needle head at apredefined needle-lift range.
 15. A mixed-mode fuel injector accordingto claim 2, wherein different shapes of fuel sprays are generated bychanging the magnitude of lift of said needle valve (1) and the needlevalve is arranged within the nozzle body (5) so that, at low to mediuminjection loads, fuel is mainly injected through the variable circularaperture between the needle head (3) and nozzle body (1), thus mainlyforms a conical shape spray, while at high injection loads, fuel isinjected through both the variable circular aperture between the needlehead and nozzle body and the micro-channels (6), thus forms a mixed-modeconical-multi-jet shape spray, whereby provides different atomizationdesired by engine combustion at different loads.
 16. A mixed-mode fuelinjector according to claim 2, wherein different shapes of fuel spraysare generated by changing the magnitude of lift of said needle valve (1)and the needle valve is arranged within the nozzle body (5) so that, atlow to medium injection loads, fuel is mainly injected through thevariable circular aperture between the needle head (3) and nozzle body,thus mainly forms a conical shape spray, while at high injection loads,the needle head can completely or partially block the variable circularaperture, whereby fuel is fully or mainly injected through themicro-channels (6), which can be open channels or closed channelsdepending on penetration needs, thus mainly forms conventionalmulti-hole sprays at high loads, whereby provides different penetrationdesired by engine combustion at different loads.
 17. A mixed-mode fuelinjector according to claim 1 or 2, wherein the fuel channel between theneedle valve (1) and the nozzle body (5) is of converging-divergingshape and by lifting said needle valve at different magnitudes, theminimum cross-section is at the sealing surface during the early stageof fuel injection, the minimum cross-section is at saidmicro-variable-circular-orifice (4) or at the sealing surface during themiddle stage of fuel injection, and the minimum cross-section is at thesealing surface again during the late stage of fuel injection, wherebyit has means of ensuring fine atomization during all fuel injectionstages.
 18. A mixed-mode fuel injector according to claim 1 or 2,wherein the angle between the centerline of the conical surface (C) andthe centerline of the nozzle body (5) is approximately 0-15 degrees,depending on an angle between a centerline of the fuel injector and acenterline of a piston in an engine cylinder.
 19. A mixed-mode fuelinjector according to any of the preceding claims, wherein the fuelinjected is one or more of diesel fuels, gasoline fuels, alternativefuels, mixtures of water and fuels, pure water or liquid exhaustcleaning additives in which case, the fuel injector is a general purposeinjector.
 20. A mixed-mode fuel injector according to claim 1, whereinthe needle valve (1) is passively driven by high fuel pressure whichprovides said driving means.
 21. A mixed-mode fuel injector according toclaim 1, wherein the needle valve (1) is actively driven by an actuatorwhich provides said driving means.
 22. A mixed-mode fuel injectoraccording to claim 21, wherein the actuator is a solenoid or a piezoactuator.
 23. A mixed-mode fuel injector, which has amicro-variable-circular-orifice (MVCO) comprising a variable circularring aperture and multiple-micro-channels as in claim 2, wherein theMVCO is used as a sole orifice or in-combination with other multi-holeconventional orifice.